Blood samples are often taken by inserting one end of a double-ended cannula into the vein of the person or animal from which the blood sample is drawn. The other end of the cannula is inserted through a rubber stopper sealed in one end of an evacuated sample tube. The reduced pressure in the sample tube quickly draws the required amount of blood sample, and this procedure may be repeated for several stoppered tubes until the required number of separate samples are taken. Thereafter, the cannula is withdrawn from the vein, and a cotton pad or the like is pressed against the puncture wound to prevent further bleeding. After sufficient time has elapsed to ensure coagulation, the cotton pad is removed and replaced by a band-aid or the like until the puncture heals.
After the cannula is withdrawn, the exposed scarf of the cannula can result in inadvertent puncture to nurses, physicians, or technicians. In the past, such punctures were of concern because of hepatitis. However, with the onset of the acquired immune deficiency syndrome (AIDS), a puncture wound from a contaminated cannula exposes personnel to the risk of contracting AIDS, an even deadlier disease.
The present invention reduces this risk by providing a protective device which permits the cannula to be retracted into a sheath as the cannula is withdrawn from the vein. With the cannula in the retracted position, personnel are protected from inadvertent puncture by a contaminated cannula, and without having to slip a separate cover over the contaminated cannula, as has been past practice with prior art blood drawing devices.